1. Field of the Invention
The invention pertains to the field of automotive transmissions. More particularly, the invention pertains to an automotive transmission with orbital gearing and a variable web-rotating device.
2. Description of Related Art
Hydraulic pumps and motors with adjustable swash plates have been discussed for use in automotive transmissions for decades, but there have been difficulties in building a hydraulic pump and motor that is both lightweight and powerful enough at the speeds and pressures necessary for use in an automobile. Traditionally, hydraulic pump/motors with adjustable swash plates have a fixed swash and a rotating cylinder block. This arrangement works well for pump/motors for applications such as golf carts and machinery, but for high pressure, high speed use in automobiles a rotating cylinder block is too large, too heavy, and too inefficient. While prior art relating to hydraulic machines has disclosed stationary cylinder blocks and split swash plates for nearly a century, no designs have proven commercially successful for use with the combination of high speeds and pressures required for automotive drives. The problem has primarily resided in the difficulty of providing a sufficiently stable piston/swash interface.
In U.S. Pat. No. 5,440,878, “VARIABLE HYDRAULIC MACHINE”, issued Aug. 15, 1995 to Gleasman et al., the piston-swash interface problem is addressed. Long dog bones interconnect the pistons and the swash, and to prevent the collapse of the dog bones under rotational stresses, the wobbler of the swash is supported by a gimbal structure. A full gimbal structure may be used with the fixed angle swash plates used on the motors, but a half-gimbal is used on the variable angle pumps. Prototypes of these machines exhibited undesirable vibrations and pulsations, indicating that the hydraulic machine could be improved.
In U.S. Pat. No. 5,513,553, “HYDRAULIC MACHINE WITH GEAR-MOUNTED SWASH-PLATE”, issued May 7, 1996 to Gleasman et al., an alternative to the gimbal is described. A spherical gear with spherical gear teeth meshes with gear teeth on the wobbler to stabilize the dog bones and wobbler by providing additional points of contact in comparison to the half-gimbal. This design, however, proved to be complicated to manufacture.
In U.S. Published Application No. 2004/0168567, “LONG-PISTON HYDRAULIC MACHINES”, published Sep. 2, 2004 to Gleasman et al., the dog bones are replaced with long pistons and the gimbal and spherical gearing are eliminated. Spring pressure “hold down” is used to maintain the shoes of the long pistons in contact with the wobbler. No restraint is required to prevent collapse, since the long pistons do not collapse under rotational stresses or in the absence of hydraulic pressure. However, there is rotational stress placed on the wobbler by the high speed of rotation of the rotor, and the effects of this stress cause undesirable inertial rotation of the wobbler.
There is a need in the art for variable hydraulic pumps and motors powerful, efficient, lightweight, and small enough to be appropriate for automotive transmission use.
In U.S. Pat. No. 6,748,817, “TRANSMISSION WITH MINIMAL ORBITER”, issued Jun. 15, 2004 to Gleasman et al., a variable pump and motor are combined with a gear orbiter to form an infinitely variable transmission. In this transmission, as the speed of the hydraulic motor increases, the output shaft speed increases and the speed of the vehicle increases.
Although an internal combustion engine is the industry standard for automobiles in the United States, several major automobile manufacturers are researching a homogeneous-charge-compression-ignition (HCCI) engine. In a conventional gasoline engine, the air-fuel mixture is ignited by a spark plug to create power. In an HCCI engine, similar to in a diesel engine, a piston compresses the air-fuel mixture to increase its temperature until it ignites. It is estimated that an HCCI engine is capable of a 30% increase in fuel economy over a standard gasoline internal combustion engine. A major hurdle for implementation of HCCI technology in automobiles is a difficulty in controlling the combustion at low and high engine speeds.
There is a need in the art for a transmission, which provides the necessary power to run an automobile while allowing its engine speed to remain in a relatively narrow low-to-moderate range where the combustion in HCCI engines is more easily controlled. Such a transmission allows implementation of more fuel efficient HCCI engines on gasoline-powered vehicles.